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ignition module troubleshoot

Carrier
M# 58GS050-EB
S#58GS-050-161EB

Owner call me to take a look at his furnace. He said he have been turning the power switch off and on to reset the system when the furnace wont recycle. I took a look at it on start up and electronic igniter will spark and lit the pilot but the igniter will not shut off until 20 minutes later. Polit will stay on for about 1-2 minute before the burner are lit. So my question is " is the ignition moduel faulty? or is there a flame sensor and is it faulty?

If the igniter acts as a flame sensor, maybe it's failing. That must be an old furnace, some of those had a three wire pilot which had a bimetal strip that turns on the main burner when it gets hot enough to turn on the power to the gas valve.

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“Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

If you replace the 3 wire pilot, dont use the Robert Shaw after market brand, use OEM...the RS's fail in about a year. Someone posted the proper way to check a 3 wire pilot a few years back...might want to do a search on the topic.

After the pilot flame is lit on the 3WP, it heats up a bimetel switch that closes the circuit for the main valve. I believe they both stay on until the heat is satisfied?....been a while.

A good indication of a bad 3WP is the main burners dropping out and coming back on. Proven by seeing the voltage drop out to the MV useing your meter.

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Once the pilot is lit you can unplug the harness, then jumping out two of the pins on the harness will bring on main flame.....problem is I can't remember which two without seeing the diagram, but yellow to green seems to sound familiar.

I give those pilots 1 to 2 minutes Max to make the switch and those warp switches tend to stick....90% of the time its just a dirty pilot orifice, but usually end up replacing it to prevent a callback.

most electronic ignition modules will lockout if flame not sensed after a set period of time ... with out knowing all the facts , it sounds like it is locking out , thats why you have to reset it ... secondly if it is igniting for 20 mins that is also an issue it should lock out much sooner than that about 30 secs to one minute max off the top of my head. ... you don't want chamber filling with gas ,,, the boom effect ... as one of the posts suggest get the manuals the answers and trouble shooting procedures you seek should be there .. good luck